Task 1 - Establish and Operate the Tall Buildings Project Advisory Committee (TPAC)

Transcription

1 The Tall Buildings Initiative Guidelines for Performance-Based Seismic Design of Tall Buildings - A summary of the development and dissemination process - Final Report Pankow Grant Agreement No December 2011 INTRODUCTION The PEER Tall Buildings Initiative Guidelines for Performance-Based Seismic Design of Tall Buildings (TBI Guidelines, 2010) provides practical guidance for designers and building officials responsible for design and design review of tall buildings that are designed outside the prescriptive building code provisions. The TBI Guidelines was made possible by a grant from Charles Pankow Foundation. The grant succeeded in aiming focus on a timely subject, leveraging multiple funding sources, engaging leading experts and stakeholders, and conducting extensive dissemination both during and following the completion of the TBI Guidelines. This brief report summarizes the Tall Buildings Initiative and identifies the development and dissemination processes that made the TBI Guidelines project a success. THE TALL BUILDINGS INITIATIVE The Tall Buildings Initiative (TBI) was a program of the Pacific Earthquake Engineering Research Center that was developed to provide guidance for performance-based seismic design of tall buildings. It was initiated in 2006, at a time where there was a surge in the design of tall buildings in the western U.S. Many of those buildings would not easily conform to the prescriptive provisions of the building code because of programmatic or structural system considerations. Some designers had begun to develop performance-based designs that did not meet all the building code prescriptive provisions, but the development process for those buildings was hampered by lack of widely accepted guidance regarding good design practices. To meet the needs in local communities, some design guidance documents were developed by the Los Angeles Tall Buildings Structural Design Council (LATBSDC, 2005) and the Structural Engineers Association of Northern California (SEAONC, 2007). The TBI was established with the goal of developing broader consensus on performance-based design of tall buildings. The TBI got under way in August 2006 with a kickoff meeting of the TBI Project Advisory Committee (TPAC), involving leading experts from the building design, seismology, research, and building regulation communities. The TPAC established a series of tasks and task team members including the following: Task 1 - Establish and Operate the Tall Buildings Project Advisory Committee (TPAC) Task 2 - Develop consensus on performance objectives W. Holmes with C. Kircher, L. Kornfield, W. Petak, and N. Yousef Task 3 Baseline assessment of dynamic response characteristics of tall buildings J. Moehle with S. Mahin, and J. Hooper. Task 4 - Synthetically generated ground motions P. Somerville with B. Aagaard, N. Collins, and Rob Graves 1

2 Task 5 Review and validation of synthetically generated ground motions F. Naeim with N. Abrahamson, Y. Bozorgnia, B. Chiou, CB Crouse, D. Dreger, J. Hooper, N. Luco, J. Maffei, Y. Moriwaki, and Y. Zeng Task 6 - Guidelines on selection and modification of ground motions for design Y. Bozorgnia and N. Luco, with F. Naeim, N. Abrahamson, J. Hooper, and J. Maffei Task 7 - Guidelines on modeling and acceptance values J. Malley with G. Deierlein, H. Krawinkler, J. Maffei, M. Pourzanjani, and J. Wallace, managed through Applied Technology Council Task 8 Input ground motions for tall buildings with subterranean levels J. Stewart with C.B. Crouse, M. Lew, F. Ostadaan, and E. Taciroglu. Task 9 Dissemination through presentations at conferences, workshops, seminars; a project web site; and written reports and papers J. Moehle with TPAC and others. Task 10 Development of a design framework and publication of design guidelines R. Hamburger and J. Moehle with Y. Bozorgnia, C.B. Crouse, R. Klemencic, H. Krawinkler, J. Malley, F. Naeim, and J. Stewart. Task 12 - Quantification of seismic performance levels of tall buildings J. Moehle and Yousef Bozorgnia with T. Yang, J. Wallace, and F. Zareian. Task 10 was to develop the TBI Guidelines, and Task 12 was to develop a series of building designs that would test the efficacy of the TBI Guidelines. DEVELOPMENT OF THE TBI GUIDELINES The first step in the development of the TBI Guidelines was to establish the project working group. Ron Hamburger of Simpson Gumpertz & Heger and Jack Moehle (UC Berkeley) were selected as Co-Chairs. The remaining project team members were selected to ensure a balance among geographic regions, technical disciplines, and academic versus practitioner backgrounds. Working group members also represented other organizations that had developed guidelines documents (LATBSDC, 2005; SEAONC, 2007; CTBUH, 2008). Simpson Gumpertz & Heger kindly agreed to serve as the central contracting agent to develop subcontracts for individual members of the working group (except Moehle and Bozorgnia). The TBI Guidelines were developed as follows: 1. A project initiation meeting was held on 2 July At this meeting, we developed a detailed work plan, a project schedule, and a preliminary outline for the guidelines. Mr. Robert Tener of the Pankow Foundation participated in this meeting. 2. During July 2008, project team members began to review available resources, including materials developed by the TBI. The team then compiled an expanded outline that included a section-by-section breakdown of the guidelines with a description of the material to be covered. 2

3 This was distributed to the team for review in August A meeting by teleconference was held to review this material to facilitate progress towards production of a first draft. 3. In September 2008, we began negotiations with representatives of the California Seismic Safety Commission to develop a companion project (Task 12) to quantify performance of buildings designed by prescriptive code provisions and by the TBI Guidelines. 4. We next compiled a first full draft of the TBI Guidelines, which was reviewed during an all-day project team meeting on 31 October The first draft of the TBI Guidelines was presented at a community workshop held on 19 January 2009 in Los Angeles. The workshop provided an opportunity for expert practitioners, code officials, and researchers to comment on the Guidelines. Following the workshop, the collected comments were incorporated into the Guidelines. 6. We next embarked on a building design case study to test and refine the TBI Guidelines. Three different structural systems were selected (RC core-only tower, RC dual system, and steel buckling-restrained braced frame), and each was assigned to a different structural engineering design firm (Magnusson Klemencic Associates, Seattle; Englekirk & Sabol Consulting Engineers, Santa Ana; and Simpson Gumpertz & Heger, San Francisco, respectively). For each building, a code-confirming design and two performance-based designs were done. The third design conformed to the TBI Guidelines. A cost estimator evaluated building initial costs and assisted in developing repair costs for projected damage states. Finally, the nine different building designs were analyzed by three different researcher teams (UC Berkeley, UCLA, and UC Irvine) to quantify future performance. 7. In parallel with the building design case study, and in consideration of the case study results, we continued to refine the TBI Guidelines through November The final version of the TBI Guidelines was published in November DISSEMINATION OF THE TBI GUIDELINES It was important to engage the practicing and research communities in the development of the TBI Guidelines so that they would be more readily accepted upon completion. The major dissemination activities included the following: 1. We introduced the TBI during a workshop of the Los Angeles Tall Buildings Structural Design Council in September 2007, including an introduction to the TBI Guidelines development project. 2. We conducted a community workshop in Los Angeles in January At this time, we had completed a first draft of the TBI Guidelines, but we were open to revisions based on comments received. The most important recommendations related to (a) damping and return period for use in the serviceability level check and (b) use of the building code minimum base shear strength. 3. We made formal presentations to the California Seismic Safety Commission on October 2009, August 2010, and January

4 4. We presented results of the building case studies at a special session of the LATBSDC Annual Meeting in May We conducted a 4-hour public workshop co-organized with the Structural Engineers Association of Washington in Seattle in October Main participants were engineers and building officials from the Seattle area. We repeated the 4-hour public workshop at a special session of the PEER Annual Meeting in San Francisco in October We released the final version of the TBI Guidelines in November The Guidelines were presented in an attractive, specially bound format that was mailed to a wide constituency. We also made the Guidelines available online at no cost. See 7. In two evening sessions in April 2011, co-sponsored by SEAONC, we conducted a public workshop on the TBI and the TBI Guidelines. Main participants were engineers and building officials from the Bay Area. We repeated this workshop in Long Beach in September 2011, in an event co-sponsored with SEAOSC. 8. We made an invited hour-long presentation of the TBI Guidelines to the Seismology Committee of the Structural Engineers Association of California in September In October 2011, we reviewed recommended code change proposals with representatives of code-writing committees ACI 318 and ASCE-7. In addition, we established and maintain a web site where all the activities of the TBI can be reviewed. Two popular downloads are the TBI Guidelines ( and Guidelines on Modeling and Acceptance Criteria ( Various other presentations on the TBI and the TBI Guidelines have been made, including: presentations to the Los Angeles Tall Buildings Structural Design Council (5/08 and 9/08); ISO-TC7 plenary presentation, Los Angeles (3/08); ACI Convention, Puerto Rico (10/07); 8 th Pacific Conference on Earthquake Engineering, Singapore (8/08); 14 th World Conference on Earthquake Engineering (2 presentations), Beijing (10/08); 9 th US National Conference on Earthquake Engineering, Toronto (7/10); and the COSMOS Annual Meeting (11/10). KEY SUCCESS FACTORS AND LESSONS LEARNED Key success factors included: 1. This was a timely topic of great interest to the profession. The TBI Guidelines were destined to affect not only the design of tall buildings, but designs of other buildings as well, so the development activity garnered much attention in the professional community. 2. The topic was ripe for completion. Much research had been done on this subject through the TBI (funding by others), there was much recent professional practice experience, and the end product was readily and clearly envisioned. In other words, the end zone was within sight and it promised a big payoff. 3. The project was highly leveraged, with funding and in-kind contributions from many other players. There was no doubt of the community interest and support for this project. 4

5 4. The industry champion was engaged at the beginning and stayed engaged through the very end. The project team also included other stakeholders whose involvement in the project ensured that it was well grounded. 5. The project maintained a steady and highly visible dissemination program. As a result, the stakeholders (practicing engineers and building officials) were ready for the final product when it was published. 6. The PI had strong ties in the research and practice sides of the problem being studied. 7. Charles Pankow Foundation was flexible in allowing additional time to fully develop the final product (the TBI Guidelines). The Guidelines could have been pushed out the door a year earlier, but the extra year enabled the development team to produce a better product that is now more widely embraced by the community. One recommendation for improving the process is to require the PI to make presentations to the Board or Advisory Committee on a more regular basis. Knowing that there are deliverables around the corner is the best incentive to keep a busy PI working on the project deliverables. REFERENCES TBI Guidelines Tall Buildings Initiative Guidelines for Performance-Based Seismic Design of Tall Buildings, Pacific Earthquake Engineering Research Center, SEAONC Recommended Administrative Bulletin on the Seismic Design & Review of Tall Buildings Using Non-Prescriptive Procedures, Structural Engineers Association of Northern California. LATBSDC An Alternative Procedure for Seismic Analysis and Design of Tall Buildings Located in the Los Angeles Region, Los Angeles Tall Buildings Structural Design Council. CTBUH, Recommendations for the Seismic Design of High-rise Buildings, Council on Tall Buildings in the Urban Habitat. 5